<!doctype html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>Document</title>
	<script type="text/javascript">

		window.onload = function  (argument) {
			btn = document.getElementById('btn');

			btn.onclick = function  (argument) {
				if(btn.value == "停止"){
					btn.value = "开始";
				}else{
					btn.value = "停止";
				}
			}
		}

	</script>
</head>
<body>
	<input id="btn" type="button" value="开始">
</body>
</html>